Grids for selective transmission of electromagnetic radiation may be used for example in medical imaging devices such as computed tomography scanners (CT), standard X-ray scanners like C-arm, mammography, etc., single photon emission computed tomography devices (SPECT) or Positron Emission Tomography scanners (PET). Other devices, such as non-destructive X-ray testing devices, may also use such grids. The grid may be positioned between a source of electromagnetic radiation such as X-ray radiation and a radiation-sensitive detection device. For example, in a CT scanner, the source of electromagnetic radiation may be an X-ray tube whereas in SPECT/PET a radioactive isotope injected into a patient may form the source of electromagnetic radiation. The radiation-sensitive detection device may be any arbitrary radiation detector such as a CCD-device, a scintillator based detector, a direct converter etc. A grid may be used to selectively reduce the content of a certain kind of radiation that must not impinge onto the radiation-sensitive detection device. The radiation reduction is usually being realized by means of radiation absorption. In a CT scanner, the grid may be used to reduce the amount of scattered radiation that is generated in an illuminated object as such scattered radiation may deteriorate the medical image quality. As today's CT scanners often apply cone-beam geometry, hence illuminate a large volume of an object, the amount of scattered radiation is often superior to the amount of the medical information carrying non-scattered primary radiation. For example, scattered radiation can easily amount to up to 90% or more of the overall radiation intensity, depending on the object.
Therefore, there is a large demand for grids that efficiently reduce scattered radiation. Grids that do fulfil this demand may be grids that have radiation absorbing structures in two dimensions that are called two-dimensional anti-scatter-grids (2D ASG). As such two-dimensional anti-scatter-grids may need to have transmission channels that are focussed to a focal spot of the radiation source that emits the primary radiation which shall be allowed to be transmitted through the grid, it may be time-consuming and costly to manufacture such grid.
WO 2008/007309 A1, filed by the same applicants as the present application, describes a grid for selective transmission of electromagnetic radiation with structural elements built by selective laser sintering. Therein, a method for manufacturing a grid comprises the step of growing at least a structural element by means of selective laser sintering from a powder material, particularly a powder of an essentially radiation-opaque material. Selective laser sintering allows for a large design freedom. Having a structural element that is built by selective laser sintering, the grid can be a highly complex three-dimensional structure that is not easily achievable by conventional moulding or milling techniques.
However, the mechanical stability as well as the radiation-absorbing properties of conventional sintered grids may have to be further improved. Furthermore, the manufacturing of such sintered grids may have to be further simplified.